'96 Johnson 115 Piston/Head damage Pics

[crappie_condo]

Long time reader, First time poster. I would like some opinions from the experts on what to do about cyl #1. Little history: Bought boat last spring, Premix 50:1, VRO disabled, Carbs gummed, I rebuilt, idle a bit touchy, but ran great. Also de-carbed engine. I was coming into the dock the other day and engine started missing. Pulled the plugs to find cyl #1 electrode bent down. Compression test: 115 psi all 4 cyl. Pulled the head to inspect and found damage to piston and head. See pics. WOT RPM = 5600 avg. load. It looks like the ring broke at the top and caused the damage. Why did the ring break?? Carbon, coking?? Thanks in advance...<br />

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[WillyBWright]

Re: '96 Johnson 115 Piston/Head damage Pics

Welcome to iboats.<br /><br />Your diagnosis sounds likely. Only way to know for sure is to remove the pistons and confirm it. It's amazing how often these failures are blamed on the VRO. Since yours was unfortunately disabled, nobody can blame this one on that.<br /><br />A few things exacerbate coking. Rich carburetion, rich oil mixture, alcohol in the gas, improper oil. Before rebuilding, you might want to look back and see if you can surmise as to which one(s) contributed to the failure. In the future, an annual decarbonizing could prevent a repeat whether there's a motor problem or not.

 

[crappie_condo]

Re: '96 Johnson 115 Piston/Head damage Pics

Thanks for the input. I forgot to metion when I first bought the boat, it had a 19 pitch prop. The 19 pitch prop only gave me around 5000 to 5200 RPM @ WOT. I doubt the previous owner did any de-carbing and after 9 years of running low RPMs maybe that did it. I'm debating on taking it somewhere or doing it myself, not much time with working hours lately. I've had my dad's 55hp Rude down to the crankshaft, but never a complete overhaul. Thanks again for the info. this is a great Board!!!

 

[R.Johnson]

Re: '96 Johnson 115 Piston/Head damage Pics

Looking at the bottom picture! Im wondering if the piston ring retaining pin did'nt come out.

 

[OBJ]

Re: '96 Johnson 115 Piston/Head damage Pics

Bet it did RJ.....just had one a month ago...looked the same....pin gone.<br /><br />condo...the head is pretty well trashed...might consider a used replacement. I'm not sure if a machinist could clean the head up or not......that's a thought I never gave a thought to.....can these be cleaned up by a machinist with out hurting the head or engine performance??

 

[jy118lfd]

Re: '96 Johnson 115 Piston/Head damage Pics

Looks like the motor was lugged and 5100 is luggung. The piston overheays and cokes up pushing the rings out into the ports. Or the piston gets to hot from lugging and the pin works out actually it goes into the piston and the rings turn trip on the port and breaks out the ring land.<br /><br />I think you problem was the latter. If and when you fix it make sure you prop it for 5800 with a light load.

 

[rodbolt]

Re: '96 Johnson 115 Piston/Head damage Pics

hello<br /> the head looks easy to fix. no worries a ball burr on a die grinder and 10 min. sometime in the mid nineties OMC moved the piston ring retaining pin from the bottom of the ring groove tothe top. why i have no clue. but since then the pin/ring failure dramatically increased. and until they move it back I dont use the factory pistons on a crossflow unless its a warrenty motor. we statred noticing a large failure rate for no obvious reason about 97-98. seems if anything went wrong the pin would fall out or the ring would ride over it. if you use factory pistons on the overhaul make sure the cyls are at the factory spec and not the service limit

 

[crappie_condo]

Re: '96 Johnson 115 Piston/Head damage Pics

OK Talked to a couple of different shops. Shop #1. $2,100 Bore all 4 cyl. go back with forged pistons and some special type rings(says you can almost tie in a knot without breaking). He does his own machine work. This also includes carb. overhaul, water pump, t-stats and lake test. 90 day warranty. Shop #2. $2,600 Bore all 4 cyl. go back with my choice of piston. Machine work is outsourced. Also includes carb. overhaul, water pump, t-stats and lake test. 1yr warranty. Is it common for the machine work to be kept in-house?? Is a 90 day warranty fairly standard on a powerhead rebuild? I was told if anything were to fail, it would happen before 90 days. I guess that mainly depends on how many hours you put on it... Does anyone recommend forged pistons and any kind of special type rings??

 

[rodbolt]

Re: '96 Johnson 115 Piston/Head damage Pics

hello<br /> I give a 1 yr warrenty on the mechanicals on my rebuilds. I wont cover a bad solinoid or pack unless it was replaced at rebuild. I alwas do a gearcase teardown as part of it. a standard v4 rebuild is in the 25-2800 dollar range. I replace all the bearings,rod bolts, seals, recirc valves, carbs get rebuilds and new fuel/OMS pumps and lines, a fuel system check and a cooling system overhaul a dyno check and a 2 hour water test. its also a good time to test all hull systems and warning horns. its not difficult. some shops have the boring and honing equipment. I dont at my shop but a friends shop does. he has been an OMC factory autherized resleeve boring center until OMC went belly up. I use sireea pistons on crossflow motors cause I dont like the design of the factory ring locating pins now. BRP may have changed them back. by doing a dyno run it allows me to check wot timing and insure the engine makes power and the hull tach is reasonably accurate. by doing the water test I insure that its propped/set up correctly.

 

[crappie_condo]

Re: '96 Johnson 115 Piston/Head damage Pics

rodbolt- Dam'n that sounds great, too bad I don't live in your area, you would definately get my business. I think I will go with shop #1, I've heard good things about this guy and he builds racing outboards. He is backed up about 4wks, so I hope it is new busniess and NOT comebacks!!LOL Do the Wiseco pistons have the same design of the ring locating pins as a stock piston?? Thanks for the info. and I will keep everyone posted...

 

[crappie_condo]

Re: '96 Johnson 115 Piston/Head damage Pics

Is it true that each cylinder may have a different size jet in the Carb?? I was told cyl#4 may have a bigger jet because it is the last cyl to be cooled in my motor? I overhauled the Carbs and thought the jets (I.E. high speed jets 2 brl carb) would be the same coming out of 1 carb. Is this fact or someone blowing smoke??

 

[Dhadley]

Re: '96 Johnson 115 Piston/Head damage Pics

Thats typical coking damage. Nothing out of the ordinary. Just get the r's up as the guys mentioned or make sure you decarb often if your not going to change the set up.<br /><br />The ring design on the Wiseco's is different than the OMC/BRP pistons.